# coding=utf-8

# Copyright 2018 The Google AI Language Team Authors and The HuggingFace Inc. team.

# Copyright (c) 2018, NVIDIA CORPORATION.  All rights reserved.

#

# Licensed under the Apache License, Version 2.0 (the "License");

# you may not use this file except in compliance with the License.

# You may obtain a copy of the License at

#

#     http://www.apache.org/licenses/LICENSE-2.0

#

# Unless required by applicable law or agreed to in writing, software

# distributed under the License is distributed on an "AS IS" BASIS,

# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

# See the License for the specific language governing permissions and

# limitations under the License.

"""PyTorch BERT model. """



from __future__ import absolute_import, division, print_function, unicode_literals



import logging

import math

import os

import sys



import torch

from torch import nn

from torch.nn import CrossEntropyLoss, MSELoss



from .modeling_utils import PreTrainedModel, prune_linear_layer

from .configuration_bert import BertConfig

from .file_utils import add_start_docstrings



logger = logging.getLogger(__name__)



BERT_PRETRAINED_MODEL_ARCHIVE_MAP = {

    'bert-base-uncased': "https://s3.amazonaws.com/models.huggingface.co/bert/bert-base-uncased-pytorch_model.bin",

    'bert-large-uncased': "https://s3.amazonaws.com/models.huggingface.co/bert/bert-large-uncased-pytorch_model.bin",

    'bert-base-cased': "https://s3.amazonaws.com/models.huggingface.co/bert/bert-base-cased-pytorch_model.bin",

    'bert-large-cased': "https://s3.amazonaws.com/models.huggingface.co/bert/bert-large-cased-pytorch_model.bin",

    'bert-base-multilingual-uncased': "https://s3.amazonaws.com/models.huggingface.co/bert/bert-base-multilingual-uncased-pytorch_model.bin",

    'bert-base-multilingual-cased': "https://s3.amazonaws.com/models.huggingface.co/bert/bert-base-multilingual-cased-pytorch_model.bin",

    'bert-base-chinese': "https://s3.amazonaws.com/models.huggingface.co/bert/bert-base-chinese-pytorch_model.bin",

    'bert-base-german-cased': "https://s3.amazonaws.com/models.huggingface.co/bert/bert-base-german-cased-pytorch_model.bin",

    'bert-large-uncased-whole-word-masking': "https://s3.amazonaws.com/models.huggingface.co/bert/bert-large-uncased-whole-word-masking-pytorch_model.bin",

    'bert-large-cased-whole-word-masking': "https://s3.amazonaws.com/models.huggingface.co/bert/bert-large-cased-whole-word-masking-pytorch_model.bin",

    'bert-large-uncased-whole-word-masking-finetuned-squad': "https://s3.amazonaws.com/models.huggingface.co/bert/bert-large-uncased-whole-word-masking-finetuned-squad-pytorch_model.bin",

    'bert-large-cased-whole-word-masking-finetuned-squad': "https://s3.amazonaws.com/models.huggingface.co/bert/bert-large-cased-whole-word-masking-finetuned-squad-pytorch_model.bin",

    'bert-base-cased-finetuned-mrpc': "https://s3.amazonaws.com/models.huggingface.co/bert/bert-base-cased-finetuned-mrpc-pytorch_model.bin",

    'bert-base-german-dbmdz-cased': "https://s3.amazonaws.com/models.huggingface.co/bert/bert-base-german-dbmdz-cased-pytorch_model.bin",

    'bert-base-german-dbmdz-uncased': "https://s3.amazonaws.com/models.huggingface.co/bert/bert-base-german-dbmdz-uncased-pytorch_model.bin",

}



class focal_loss(nn.Module):

    def __init__(self, alpha=[1,1], gamma=2, num_classes = 2, size_average=True):

        """

        focal_loss损失函数, -α(1-yi)**γ *ce_loss(xi,yi)

        步骤详细的实现了 focal_loss损失函数.

        :param alpha:   阿尔法α,类别权重.      当α是列表时,为各类别权重,当α为常数时,类别权重为[α, 1-α, 1-α, ....],常用于 目标检测算法中抑制背景类 , retainnet中设置为0.25

        :param gamma:   伽马γ,难易样本调节参数. retainnet中设置为2

        :param num_classes:     类别数量

        :param size_average:    损失计算方式,默认取均值

        """



        super(focal_loss,self).__init__()

        self.size_average = size_average

        if isinstance(alpha,list):

            assert len(alpha)==num_classes   # α可以以list方式输入,size:[num_classes] 用于对不同类别精细地赋予权重

            print("Focal_loss alpha = {}, 将对每一类权重进行精细化赋值".format(alpha))

            self.alpha = torch.Tensor(alpha)

        else:

            assert alpha<1   #如果α为一个常数,则降低第一类的影响,在目标检测中为第一类

            print(" --- Focal_loss alpha = {} ,将对背景类进行衰减,请在目标检测任务中使用 --- ".format(alpha))

            self.alpha = torch.zeros(num_classes)

            self.alpha[0] += alpha

            self.alpha[1:] += (1-alpha) # α 最终为 [ α, 1-α, 1-α, 1-α, 1-α, ...] size:[num_classes]

        self.gamma = gamma



    def forward(self, preds, labels):

        """

        focal_loss损失计算

        :param preds:   预测类别. size:[B,N,C] or [B,C]    分别对应与检测与分类任务, B 批次, N检测框数, C类别数

        :param labels:  实际类别. size:[B,N] or [B]

        :return:

        """

        # assert preds.dim()==2 and labels.dim()==1

        preds = preds.view(-1,preds.size(-1))

        self.alpha = self.alpha.to(preds.device)

        preds_softmax = torch.softmax(preds, dim=1) # 这里并没有直接使用log_softmax, 因为后面会用到softmax的结果(当然你也可以使用log_softmax,然后进行exp操作)

        preds_logsoft = torch.log(preds_softmax)

        preds_softmax = preds_softmax.gather(1,labels.view(-1,1))   # 这部分实现nll_loss ( crossempty = log_softmax + nll )

        preds_logsoft = preds_logsoft.gather(1,labels.view(-1,1))

        alpha = self.alpha.gather(0,labels.view(-1))

        loss = -torch.mul(torch.pow((1-preds_softmax), self.gamma), preds_logsoft)  # torch.pow((1-preds_softmax), self.gamma) 为focal loss中 (1-pt)**γ

        loss = torch.mul(alpha, loss.t())

        if self.size_average:

            loss = loss.mean()

        else:

            loss = loss.sum()

        return loss


### /* Start Insert Code For ERNIE */

class BertEntitySelfAttention(nn.Module):
    def __init__(self, config):
        super(BertEntitySelfAttention, self).__init__()
        if config.hidden_size % config.num_attention_heads != 0:
            raise ValueError(
                "The hidden size (%d) is not a multiple of the number of attention "
                "heads (%d)" % (config.hidden_size, config.num_attention_heads))
        self.num_attention_heads = config.num_attention_heads
        self.attention_head_size = int(config.hidden_size / config.num_attention_heads)
        self.all_head_size = self.num_attention_heads * self.attention_head_size
        self.query = nn.Linear(config.hidden_size, self.all_head_size)
        self.key = nn.Linear(config.hidden_size, self.all_head_size)
        self.value = nn.Linear(config.hidden_size, self.all_head_size)
        self.dropout = nn.Dropout(config.attention_probs_dropout_prob)
    def transpose_for_scores(self, x):
        new_x_shape = x.size()[:-1] + (self.num_attention_heads, self.attention_head_size)
        x = x.view(*new_x_shape)
        return x.permute(0, 2, 1, 3)
    def forward(self, hidden_states, attention_mask):
        mixed_query_layer = self.query(hidden_states)
        mixed_key_layer = self.key(hidden_states)
        mixed_value_layer = self.value(hidden_states)

        query_layer = self.transpose_for_scores(mixed_query_layer)
        key_layer = self.transpose_for_scores(mixed_key_layer)
        value_layer = self.transpose_for_scores(mixed_value_layer)

        # Take the dot product between "query" and "key" to get the raw attention scores.
        attention_scores = torch.matmul(query_layer, key_layer.transpose(-1, -2))
        attention_scores = attention_scores / math.sqrt(self.attention_head_size)
        # Apply the attention mask is (precomputed for all layers in BertModel forward() function)
        attention_scores = attention_scores + attention_mask

        # Normalize the attention scores to probabilities.
        attention_probs = nn.Softmax(dim=-1)(attention_scores)

        # This is actually dropping out entire tokens to attend to, which might
        # seem a bit unusual, but is taken from the original Transformer paper.
        attention_probs = self.dropout(attention_probs)

        context_layer = torch.matmul(attention_probs, value_layer)
        context_layer = context_layer.permute(0, 2, 1, 3).contiguous()
        new_context_layer_shape = context_layer.size()[:-2] + (self.all_head_size,)
        context_layer = context_layer.view(*new_context_layer_shape)
        return context_layer

class BertAttention_simple(nn.Module):
    def __init__(self, config):
        super(BertAttention_simple, self).__init__()
        self.self = BertEntitySelfAttention(config)
        self.output = BertEntitySelfOutput(config)
    def forward(self, input_tensor, attention_mask):
        self_output = self.self(input_tensor, attention_mask)
        attention_output = self.output(self_output, input_tensor)
        return attention_output

class BertEntitySelfOutput(nn.Module):
    def __init__(self, config):
        super(BertEntitySelfOutput, self).__init__()
        self.dense = nn.Linear(config.hidden_size, config.hidden_size)
        self.LayerNorm = BertLayerNorm(config.hidden_size, eps=1e-12)
        self.dropout = nn.Dropout(config.hidden_dropout_prob)

    def forward(self, hidden_states, input_tensor):
        hidden_states = self.dense(hidden_states)
        hidden_states = self.dropout(hidden_states)
        hidden_states = self.LayerNorm(hidden_states + input_tensor)
        return hidden_states
    
class BertEntityIntermediate(nn.Module):
    def __init__(self, config):
        super(BertEntityIntermediate, self).__init__()
        self.dense = nn.Linear(config.hidden_size, config.intermediate_size)
        self.dense_ent = nn.Linear(100, config.intermediate_size)
        #self.dense_1 = nn.Linear(config.hidden_size, 200)
        #self.dense_1_ent = nn.Linear(100, 200)
        self.intermediate_act_fn = ACT2FN[config.hidden_act] \
            if isinstance(config.hidden_act, str) else config.hidden_act
    def forward(self, hidden_states, hidden_states_ent):
        hidden_states_ = self.dense(hidden_states)
        hidden_states_ent_ = self.dense_ent(hidden_states_ent)
        hidden_states = self.intermediate_act_fn(hidden_states_+hidden_states_ent_)
        return hidden_states#, hidden_states_ent
    
class BertEntityOutput(nn.Module):
    def __init__(self, config):
        super(BertEntityOutput, self).__init__()
        self.dense = nn.Linear(config.intermediate_size, config.hidden_size)
        self.dense_ent = nn.Linear(config.intermediate_size, 100)
        self.LayerNorm = BertLayerNorm(config.hidden_size, eps=1e-12)
        self.LayerNorm_ent = BertLayerNorm(100, eps=1e-12)
        self.dropout = nn.Dropout(config.hidden_dropout_prob)

    def forward(self, hidden_states_, input_tensor, input_tensor_ent):
        hidden_states = self.dense(hidden_states_)
        hidden_states = self.dropout(hidden_states)
        hidden_states = self.LayerNorm(hidden_states + input_tensor)

        hidden_states_ent = self.dense_ent(hidden_states_)
        hidden_states_ent = self.dropout(hidden_states_ent)
        hidden_states_ent = self.LayerNorm_ent(hidden_states_ent + input_tensor_ent)

        return hidden_states, hidden_states_ent

class BertEntityAttention(nn.Module):
    def __init__(self, config):
        super(BertEntityAttention, self).__init__()
        self.self = BertEntitySelfAttention(config)
        self.output = BertEntitySelfOutput(config)

        config_ent = copy.deepcopy(config)
        config_ent.hidden_size = 100
        config_ent.num_attention_heads = 4

        self.self_ent = BertEntitySelfAttention(config_ent)
        self.output_ent = BertEntitySelfOutput(config_ent)


    def forward(self, input_tensor, attention_mask, input_tensor_ent, attention_mask_ent):
        self_output = self.self(input_tensor, attention_mask)
        self_output_ent = self.self_ent(input_tensor_ent, attention_mask_ent)
        attention_output = self.output(self_output, input_tensor)
        attention_output_ent = self.output_ent(self_output_ent, input_tensor_ent)
        return attention_output, attention_output_ent

class BertLayerMix(nn.Module):
    def __init__(self, config):
        super(BertLayerMix, self).__init__()
        self.attention = BertAttention_simple(config)
        self.intermediate = BertEntityIntermediate(config)
        self.output = BertEntityOutput(config)
    def forward(self, hidden_states, attention_mask, hidden_states_ent, attention_mask_ent, ent_mask):
        attention_output = self.attention(hidden_states, attention_mask)
        attention_output_ent = hidden_states_ent * ent_mask
        intermediate_output = self.intermediate(attention_output, attention_output_ent) # Get H_i
        layer_output, layer_output_ent = self.output(intermediate_output, attention_output, attention_output_ent) # Get W and E from H
        # layer_output_ent = layer_output_ent * ent_mask
        return layer_output, layer_output_ent

class BertLayer(nn.Module):
    def __init__(self, config):
        super(BertLayer, self).__init__()
        self.attention = BertEntityAttention(config)
        self.intermediate = BertEntityIntermediate(config)
        self.output = BertEntityOutput(config)

    def forward(self, hidden_states, attention_mask, hidden_states_ent, attention_mask_ent, ent_mask):
        attention_output, attention_output_ent = self.attention(hidden_states, attention_mask, hidden_states_ent, attention_mask_ent)
        attention_output_ent = attention_output_ent * ent_mask
        intermediate_output = self.intermediate(attention_output, attention_output_ent)
        layer_output, layer_output_ent = self.output(intermediate_output, attention_output, attention_output_ent)
        # layer_output_ent = layer_output_ent * ent_mask
        return layer_output, layer_output_ent

class BertEntPredictionHead(nn.Module):
    def __init__(self, config):
        super(BertEntPredictionHead, self).__init__()
        config_ent = copy.deepcopy(config)
        config_ent.hidden_size = 100
        self.transform = BertPredictionHeadTransform(config_ent)

    def forward(self, hidden_states, candidate):
        hidden_states = self.transform(hidden_states)
        candidate = torch.squeeze(candidate, 0)
        # hidden_states [batch_size, max_seq, dim]
        # candidate [entity_num_in_the_batch, dim]
        # return [batch_size, max_seq, entity_num_in_the_batch]
        return torch.matmul(hidden_states, candidate.t())

class BertEntityPreTrainingHeads(nn.Module):
    def __init__(self, config, bert_model_embedding_weights):
        super(BertEntityPreTrainingHeads, self).__init__()
        self.predictions = BertLMPredictionHead(config, bert_model_embedding_weights)
        self.predictions_ent = BertEntPredictionHead(config)
        self.seq_relationship = nn.Linear(config.hidden_size, 2)

    def forward(self, sequence_output, pooled_output, candidate):
        prediction_scores = self.predictions(sequence_output)
        seq_relationship_score = self.seq_relationship(pooled_output)
        prediction_scores_ent = self.predictions_ent(sequence_output, candidate)
        return prediction_scores, seq_relationship_score, prediction_scores_ent


###### /* End of Insertion */

def load_tf_weights_in_bert(model, config, tf_checkpoint_path):

    """ Load tf checkpoints in a pytorch model.

    """

    try:

        import re

        import numpy as np

        import tensorflow as tf

    except ImportError:

        logger.error("Loading a TensorFlow model in PyTorch, requires TensorFlow to be installed. Please see "

            "https://www.tensorflow.org/install/ for installation instructions.")

        raise

    tf_path = os.path.abspath(tf_checkpoint_path)

    logger.info("Converting TensorFlow checkpoint from {}".format(tf_path))

    # Load weights from TF model

    init_vars = tf.train.list_variables(tf_path)

    names = []

    arrays = []

    for name, shape in init_vars:

        logger.info("Loading TF weight {} with shape {}".format(name, shape))

        array = tf.train.load_variable(tf_path, name)

        names.append(name)

        arrays.append(array)



    for name, array in zip(names, arrays):

        name = name.split('/')

        # adam_v and adam_m are variables used in AdamWeightDecayOptimizer to calculated m and v

        # which are not required for using pretrained model

        if any(n in ["adam_v", "adam_m", "global_step"] for n in name):

            logger.info("Skipping {}".format("/".join(name)))

            continue

        pointer = model

        for m_name in name:

            if re.fullmatch(r'[A-Za-z]+_\d+', m_name):

                l = re.split(r'_(\d+)', m_name)

            else:

                l = [m_name]

            if l[0] == 'kernel' or l[0] == 'gamma':

                pointer = getattr(pointer, 'weight')

            elif l[0] == 'output_bias' or l[0] == 'beta':

                pointer = getattr(pointer, 'bias')

            elif l[0] == 'output_weights':

                pointer = getattr(pointer, 'weight')

            elif l[0] == 'squad':

                pointer = getattr(pointer, 'classifier')

            else:

                try:

                    pointer = getattr(pointer, l[0])

                except AttributeError:

                    logger.info("Skipping {}".format("/".join(name)))

                    continue

            if len(l) >= 2:

                num = int(l[1])

                pointer = pointer[num]

        if m_name[-11:] == '_embeddings':

            pointer = getattr(pointer, 'weight')

        elif m_name == 'kernel':

            array = np.transpose(array)

        try:

            assert pointer.shape == array.shape

        except AssertionError as e:

            e.args += (pointer.shape, array.shape)

            raise

        logger.info("Initialize PyTorch weight {}".format(name))

        pointer.data = torch.from_numpy(array)

    return model





def gelu(x):

    """ Original Implementation of the gelu activation function in Google Bert repo when initially created.

        For information: OpenAI GPT's gelu is slightly different (and gives slightly different results):

        0.5 * x * (1 + torch.tanh(math.sqrt(2 / math.pi) * (x + 0.044715 * torch.pow(x, 3))))

        Also see https://arxiv.org/abs/1606.08415

    """

    return x * 0.5 * (1.0 + torch.erf(x / math.sqrt(2.0)))





def gelu_new(x):

    """ Implementation of the gelu activation function currently in Google Bert repo (identical to OpenAI GPT).

        Also see https://arxiv.org/abs/1606.08415

    """

    return 0.5 * x * (1 + torch.tanh(math.sqrt(2 / math.pi) * (x + 0.044715 * torch.pow(x, 3))))





def swish(x):

    return x * torch.sigmoid(x)





def mish(x):

    return x * torch.tanh(nn.functional.softplus(x))





ACT2FN = {"gelu": gelu, "relu": torch.nn.functional.relu, "swish": swish, "gelu_new": gelu_new, "mish": mish}





BertLayerNorm = torch.nn.LayerNorm





class BertEmbeddings(nn.Module):

    """Construct the embeddings from word, position and token_type embeddings.

    """

    def __init__(self, config):

        super(BertEmbeddings, self).__init__()

        self.word_embeddings = nn.Embedding(config.vocab_size, config.hidden_size, padding_idx=0)

        self.position_embeddings = nn.Embedding(config.max_position_embeddings, config.hidden_size)

        self.token_type_embeddings = nn.Embedding(config.type_vocab_size, config.hidden_size)



        # self.LayerNorm is not snake-cased to stick with TensorFlow model variable name and be able to load

        # any TensorFlow checkpoint file

        self.LayerNorm = BertLayerNorm(config.hidden_size, eps=config.layer_norm_eps)

        self.dropout = nn.Dropout(config.hidden_dropout_prob)



    def forward(self, input_ids=None, token_type_ids=None, position_ids=None, inputs_embeds=None):

        if input_ids is not None:

            input_shape = input_ids.size()

        else:

            input_shape = inputs_embeds.size()[:-1]



        seq_length = input_shape[1]

        device = input_ids.device if input_ids is not None else inputs_embeds.device

        if position_ids is None:

            position_ids = torch.arange(seq_length, dtype=torch.long, device=device)

            position_ids = position_ids.unsqueeze(0).expand(input_shape)

        if token_type_ids is None:

            token_type_ids = torch.zeros(input_shape, dtype=torch.long, device=device)



        if inputs_embeds is None:

            inputs_embeds = self.word_embeddings(input_ids)

        position_embeddings = self.position_embeddings(position_ids)

        token_type_embeddings = self.token_type_embeddings(token_type_ids)



        embeddings = inputs_embeds + position_embeddings + token_type_embeddings

        embeddings = self.LayerNorm(embeddings)

        embeddings = self.dropout(embeddings)

        return embeddings





class BertSelfAttention(nn.Module):

    def __init__(self, config):

        super(BertSelfAttention, self).__init__()

        if config.hidden_size % config.num_attention_heads != 0:

            raise ValueError(

                "The hidden size (%d) is not a multiple of the number of attention "

                "heads (%d)" % (config.hidden_size, config.num_attention_heads))

        self.output_attentions = config.output_attentions



        self.num_attention_heads = config.num_attention_heads

        self.attention_head_size = int(config.hidden_size / config.num_attention_heads)

        self.all_head_size = self.num_attention_heads * self.attention_head_size



        self.query = nn.Linear(config.hidden_size, self.all_head_size)

        self.key = nn.Linear(config.hidden_size, self.all_head_size)

        self.value = nn.Linear(config.hidden_size, self.all_head_size)
        self.dropout = nn.Dropout(config.attention_probs_dropout_prob)



    def transpose_for_scores(self, x):
        new_x_shape = x.size()[:-1] + (self.num_attention_heads, self.attention_head_size)
        x = x.view(*new_x_shape)
        return x.permute(0, 2, 1, 3)

    def forward(self, hidden_states, attention_mask=None, head_mask=None, encoder_hidden_states=None, encoder_attention_mask=None):
        mixed_query_layer = self.query(hidden_states)
        # If this is instantiated as a cross-attention module, the keys
        # and values come from an encoder; the attention mask needs to be
        # such that the encoder's padding tokens are not attended to.
        if encoder_hidden_states is not None:
            mixed_key_layer = self.key(encoder_hidden_states)
            mixed_value_layer = self.value(encoder_hidden_states)
            attention_mask = encoder_attention_mask
        else:
            mixed_key_layer = self.key(hidden_states)
            mixed_value_layer = self.value(hidden_states)
        query_layer = self.transpose_for_scores(mixed_query_layer)
        key_layer = self.transpose_for_scores(mixed_key_layer)
        value_layer = self.transpose_for_scores(mixed_value_layer)

        # Take the dot product between "query" and "key" to get the raw attention scores.
        attention_scores = torch.matmul(query_layer, key_layer.transpose(-1, -2))
        attention_scores = attention_scores / math.sqrt(self.attention_head_size)
        if attention_mask is not None:
            # Apply the attention mask is (precomputed for all layers in BertModel forward() function)
            attention_scores = attention_scores + attention_mask

        # Normalize the attention scores to probabilities.
        attention_probs = nn.Softmax(dim=-1)(attention_scores)
        # This is actually dropping out entire tokens to attend to, which might
        # seem a bit unusual, but is taken from the original Transformer paper.
        attention_probs = self.dropout(attention_probs)
        # Mask heads if we want to
        if head_mask is not None:
            attention_probs = attention_probs * head_mask
        context_layer = torch.matmul(attention_probs, value_layer)
        context_layer = context_layer.permute(0, 2, 1, 3).contiguous()
        new_context_layer_shape = context_layer.size()[:-2] + (self.all_head_size,)
        context_layer = context_layer.view(*new_context_layer_shape)
        outputs = (context_layer, attention_probs) if self.output_attentions else (context_layer,)
        return outputs





class BertSelfOutput(nn.Module):

    def __init__(self, config):

        super(BertSelfOutput, self).__init__()

        self.dense = nn.Linear(config.hidden_size, config.hidden_size)

        self.LayerNorm = BertLayerNorm(config.hidden_size, eps=config.layer_norm_eps)

        self.dropout = nn.Dropout(config.hidden_dropout_prob)



    def forward(self, hidden_states, input_tensor):

        hidden_states = self.dense(hidden_states)

        hidden_states = self.dropout(hidden_states)

        hidden_states = self.LayerNorm(hidden_states + input_tensor)

        return hidden_states





class BertAttention(nn.Module):

    def __init__(self, config):

        super(BertAttention, self).__init__()

        self.self = BertSelfAttention(config)

        self.output = BertSelfOutput(config)

        self.pruned_heads = set()



    def prune_heads(self, heads):

        if len(heads) == 0:

            return

        mask = torch.ones(self.self.num_attention_heads, self.self.attention_head_size)

        heads = set(heads) - self.pruned_heads  # Convert to set and remove already pruned heads

        for head in heads:

            # Compute how many pruned heads are before the head and move the index accordingly

            head = head - sum(1 if h < head else 0 for h in self.pruned_heads)

            mask[head] = 0

        mask = mask.view(-1).contiguous().eq(1)

        index = torch.arange(len(mask))[mask].long()



        # Prune linear layers

        self.self.query = prune_linear_layer(self.self.query, index)

        self.self.key = prune_linear_layer(self.self.key, index)

        self.self.value = prune_linear_layer(self.self.value, index)

        self.output.dense = prune_linear_layer(self.output.dense, index, dim=1)



        # Update hyper params and store pruned heads

        self.self.num_attention_heads = self.self.num_attention_heads - len(heads)

        self.self.all_head_size = self.self.attention_head_size * self.self.num_attention_heads

        self.pruned_heads = self.pruned_heads.union(heads)



    def forward(self, hidden_states, attention_mask=None, head_mask=None, encoder_hidden_states=None, encoder_attention_mask=None):

        self_outputs = self.self(hidden_states, attention_mask, head_mask, encoder_hidden_states, encoder_attention_mask)

        attention_output = self.output(self_outputs[0], hidden_states)

        outputs = (attention_output,) + self_outputs[1:]  # add attentions if we output them

        return outputs





class BertIntermediate(nn.Module):

    def __init__(self, config):

        super(BertIntermediate, self).__init__()

        self.dense = nn.Linear(config.hidden_size, config.intermediate_size)

        if isinstance(config.hidden_act, str) or (sys.version_info[0] == 2 and isinstance(config.hidden_act, unicode)):

            self.intermediate_act_fn = ACT2FN[config.hidden_act]

        else:

            self.intermediate_act_fn = config.hidden_act



    def forward(self, hidden_states):

        hidden_states = self.dense(hidden_states)

        hidden_states = self.intermediate_act_fn(hidden_states)

        return hidden_states





class BertOutput(nn.Module):

    def __init__(self, config):

        super(BertOutput, self).__init__()

        self.dense = nn.Linear(config.intermediate_size, config.hidden_size)

        self.LayerNorm = BertLayerNorm(config.hidden_size, eps=config.layer_norm_eps)

        self.dropout = nn.Dropout(config.hidden_dropout_prob)



    def forward(self, hidden_states, input_tensor):

        hidden_states = self.dense(hidden_states)

        hidden_states = self.dropout(hidden_states)

        hidden_states = self.LayerNorm(hidden_states + input_tensor)

        return hidden_states





class BertLayer(nn.Module):

    def __init__(self, config):

        super(BertLayer, self).__init__()

        self.attention = BertAttention(config)

        self.is_decoder = config.is_decoder

        if self.is_decoder:

            self.crossattention = BertAttention(config)

        self.intermediate = BertIntermediate(config)

        self.output = BertOutput(config)



    def forward(self, hidden_states, attention_mask=None, head_mask=None, encoder_hidden_states=None, encoder_attention_mask=None):

        self_attention_outputs = self.attention(hidden_states, attention_mask, head_mask)

        attention_output = self_attention_outputs[0]

        outputs = self_attention_outputs[1:]  # add self attentions if we output attention weights



        if self.is_decoder and encoder_hidden_states is not None:

            cross_attention_outputs = self.crossattention(attention_output, attention_mask, head_mask, encoder_hidden_states, encoder_attention_mask)

            attention_output = cross_attention_outputs[0]

            outputs = outputs + cross_attention_outputs[1:]  # add cross attentions if we output attention weights



        intermediate_output = self.intermediate(attention_output)

        layer_output = self.output(intermediate_output, attention_output)

        outputs = (layer_output,) + outputs

        return outputs





class BertEncoder(nn.Module):

    def __init__(self, config):
        super(BertEncoder, self).__init__()
        self.output_attentions = config.output_attentions
        self.output_hidden_states = config.output_hidden_states
        self.layer = nn.ModuleList([BertLayer(config) for _ in range(config.num_hidden_layers)])
        self.layer_mix = BertLayerMix(config)
        self.layer_norm = BertLayerNorm(config)

    def forward(self, hidden_states, attention_mask=None, head_mask=None, encoder_hidden_states=None, encoder_attention_mask=None):
        all_hidden_states = ()
        all_attentions = ()
        for i, layer_module in enumerate(self.layer):
            if self.output_hidden_states:
                all_hidden_states = all_hidden_states + (hidden_states,)
            layer_outputs = layer_module(hidden_states, attention_mask, head_mask[i], encoder_hidden_states, encoder_attention_mask)
            hidden_states = layer_outputs[0]
            if self.output_attentions:
                all_attentions = all_attentions + (layer_outputs[1],)
        # Add last layer
        if self.output_hidden_states:
            all_hidden_states = all_hidden_states + (hidden_states,)
        outputs = (hidden_states,)
        if self.output_hidden_states:
            outputs = outputs + (all_hidden_states,)
        if self.output_attentions:
            outputs = outputs + (all_attentions,)
        return outputs  # last-layer hidden state, (all hidden states), (all attentions)





class BertPooler(nn.Module):

    def __init__(self, config):

        super(BertPooler, self).__init__()

        self.dense = nn.Linear(config.hidden_size, config.hidden_size)

        self.activation = nn.Tanh()



    def forward(self, hidden_states):

        # We "pool" the model by simply taking the hidden state corresponding

        # to the first token.

        first_token_tensor = hidden_states[:, 0]

        pooled_output = self.dense(first_token_tensor)

        pooled_output = self.activation(pooled_output)

        return pooled_output





class BertPredictionHeadTransform(nn.Module):

    def __init__(self, config):

        super(BertPredictionHeadTransform, self).__init__()

        self.dense = nn.Linear(config.hidden_size, config.hidden_size)

        if isinstance(config.hidden_act, str) or (sys.version_info[0] == 2 and isinstance(config.hidden_act, unicode)):

            self.transform_act_fn = ACT2FN[config.hidden_act]

        else:

            self.transform_act_fn = config.hidden_act

        self.LayerNorm = BertLayerNorm(config.hidden_size, eps=config.layer_norm_eps)



    def forward(self, hidden_states):

        hidden_states = self.dense(hidden_states)

        hidden_states = self.transform_act_fn(hidden_states)

        hidden_states = self.LayerNorm(hidden_states)

        return hidden_states





class BertLMPredictionHead(nn.Module):

    def __init__(self, config):
        super(BertLMPredictionHead, self).__init__()
        self.transform = BertPredictionHeadTransform(config)
        # The output weights are the same as the input embeddings, but there is
        # an output-only bias for each token.
        self.decoder = nn.Linear(config.hidden_size,
                                 config.vocab_size,
                                 bias=False)
        self.bias = nn.Parameter(torch.zeros(config.vocab_size))

    def forward(self, hidden_states):
        hidden_states = self.transform(hidden_states)
        hidden_states = self.decoder(hidden_states) + self.bias
        return hidden_states





class BertOnlyMLMHead(nn.Module):
    def __init__(self, config):
        super(BertOnlyMLMHead, self).__init__()

        self.predictions = BertLMPredictionHead(config)



    def forward(self, sequence_output):

        prediction_scores = self.predictions(sequence_output)

        return prediction_scores





class BertOnlyNSPHead(nn.Module):

    def __init__(self, config):

        super(BertOnlyNSPHead, self).__init__()

        self.seq_relationship = nn.Linear(config.hidden_size, 2)



    def forward(self, pooled_output):

        seq_relationship_score = self.seq_relationship(pooled_output)

        return seq_relationship_score





class BertPreTrainingHeads(nn.Module):

    def __init__(self, config):

        super(BertPreTrainingHeads, self).__init__()

        self.predictions = BertLMPredictionHead(config)

        self.seq_relationship = nn.Linear(config.hidden_size, 2)



    def forward(self, sequence_output, pooled_output):

        prediction_scores = self.predictions(sequence_output)

        seq_relationship_score = self.seq_relationship(pooled_output)

        return prediction_scores, seq_relationship_score





class BertPreTrainedModel(PreTrainedModel):

    """ An abstract class to handle weights initialization and

        a simple interface for dowloading and loading pretrained models.

    """

    config_class = BertConfig

    pretrained_model_archive_map = BERT_PRETRAINED_MODEL_ARCHIVE_MAP

    load_tf_weights = load_tf_weights_in_bert

    base_model_prefix = "bert"



    def _init_weights(self, module):

        """ Initialize the weights """

        if isinstance(module, (nn.Linear, nn.Embedding)):

            # Slightly different from the TF version which uses truncated_normal for initialization

            # cf https://github.com/pytorch/pytorch/pull/5617

            module.weight.data.normal_(mean=0.0, std=self.config.initializer_range)

        elif isinstance(module, BertLayerNorm):

            module.bias.data.zero_()

            module.weight.data.fill_(1.0)

        if isinstance(module, nn.Linear) and module.bias is not None:

            module.bias.data.zero_()





BERT_START_DOCSTRING = r"""    The BERT model was proposed in

    `BERT: Pre-training of Deep Bidirectional Transformers for Language Understanding`_

    by Jacob Devlin, Ming-Wei Chang, Kenton Lee and Kristina Toutanova. It's a bidirectional transformer

    pre-trained using a combination of masked language modeling objective and next sentence prediction

    on a large corpus comprising the Toronto Book Corpus and Wikipedia.



    This model is a PyTorch `torch.nn.Module`_ sub-class. Use it as a regular PyTorch Module and

    refer to the PyTorch documentation for all matter related to general usage and behavior.



    .. _`BERT: Pre-training of Deep Bidirectional Transformers for Language Understanding`:

        https://arxiv.org/abs/1810.04805



    .. _`torch.nn.Module`:

        https://pytorch.org/docs/stable/nn.html#module



    Parameters:

        config (:class:`~transformers.BertConfig`): Model configuration class with all the parameters of the model.

            Initializing with a config file does not load the weights associated with the model, only the configuration.

            Check out the :meth:`~transformers.PreTrainedModel.from_pretrained` method to load the model weights.

"""



BERT_INPUTS_DOCSTRING = r"""

    Inputs:

        **input_ids**: ``torch.LongTensor`` of shape ``(batch_size, sequence_length)``:

            Indices of input sequence tokens in the vocabulary.

            To match pre-training, BERT input sequence should be formatted with [CLS] and [SEP] tokens as follows:



            (a) For sequence pairs:



                ``tokens:         [CLS] is this jack ##son ##ville ? [SEP] no it is not . [SEP]``



                ``token_type_ids:   0   0  0    0    0     0       0   0   1  1  1  1   1   1``



            (b) For single sequences:



                ``tokens:         [CLS] the dog is hairy . [SEP]``



                ``token_type_ids:   0   0   0   0  0     0   0``



            Bert is a model with absolute position embeddings so it's usually advised to pad the inputs on

            the right rather than the left.



            Indices can be obtained using :class:`transformers.BertTokenizer`.

            See :func:`transformers.PreTrainedTokenizer.encode` and

            :func:`transformers.PreTrainedTokenizer.convert_tokens_to_ids` for details.

        **attention_mask**: (`optional`) ``torch.FloatTensor`` of shape ``(batch_size, sequence_length)``:

            Mask to avoid performing attention on padding token indices.

            Mask values selected in ``[0, 1]``:

            ``1`` for tokens that are NOT MASKED, ``0`` for MASKED tokens.

        **token_type_ids**: (`optional`) ``torch.LongTensor`` of shape ``(batch_size, sequence_length)``:

            Segment token indices to indicate first and second portions of the inputs.

            Indices are selected in ``[0, 1]``: ``0`` corresponds to a `sentence A` token, ``1``

            corresponds to a `sentence B` token

            (see `BERT: Pre-training of Deep Bidirectional Transformers for Language Understanding`_ for more details).

        **position_ids**: (`optional`) ``torch.LongTensor`` of shape ``(batch_size, sequence_length)``:

            Indices of positions of each input sequence tokens in the position embeddings.

            Selected in the range ``[0, config.max_position_embeddings - 1]``.

        **head_mask**: (`optional`) ``torch.FloatTensor`` of shape ``(num_heads,)`` or ``(num_layers, num_heads)``:

            Mask to nullify selected heads of the self-attention modules.

            Mask values selected in ``[0, 1]``:

            ``1`` indicates the head is **not masked**, ``0`` indicates the head is **masked**.

        **inputs_embeds**: (`optional`) ``torch.FloatTensor`` of shape ``(batch_size, sequence_length, embedding_dim)``:

            Optionally, instead of passing ``input_ids`` you can choose to directly pass an embedded representation.

            This is useful if you want more control over how to convert `input_ids` indices into associated vectors

            than the model's internal embedding lookup matrix.

        **encoder_hidden_states**: (`optional`) ``torch.FloatTensor`` of shape ``(batch_size, sequence_length, hidden_size)``:

            Sequence of hidden-states at the output of the last layer of the encoder. Used in the cross-attention if the model

            is configured as a decoder.

        **encoder_attention_mask**: (`optional`) ``torch.FloatTensor`` of shape ``(batch_size, sequence_length)``:

            Mask to avoid performing attention on the padding token indices of the encoder input. This mask

            is used in the cross-attention if the model is configured as a decoder.

            Mask values selected in ``[0, 1]``:

            ``1`` for tokens that are NOT MASKED, ``0`` for MASKED tokens.

"""



@add_start_docstrings("The bare Bert Model transformer outputting raw hidden-states without any specific head on top.",

                      BERT_START_DOCSTRING, BERT_INPUTS_DOCSTRING)

class BertModel(BertPreTrainedModel):

    r"""

    Outputs: `Tuple` comprising various elements depending on the configuration (config) and inputs:

        **last_hidden_state**: ``torch.FloatTensor`` of shape ``(batch_size, sequence_length, hidden_size)``

            Sequence of hidden-states at the output of the last layer of the model.

        **pooler_output**: ``torch.FloatTensor`` of shape ``(batch_size, hidden_size)``

            Last layer hidden-state of the first token of the sequence (classification token)

            further processed by a Linear layer and a Tanh activation function. The Linear

            layer weights are trained from the next sentence prediction (classification)

            objective during Bert pretraining. This output is usually *not* a good summary

            of the semantic content of the input, you're often better with averaging or pooling

            the sequence of hidden-states for the whole input sequence.

        **hidden_states**: (`optional`, returned when ``config.output_hidden_states=True``)

            list of ``torch.FloatTensor`` (one for the output of each layer + the output of the embeddings)

            of shape ``(batch_size, sequence_length, hidden_size)``:

            Hidden-states of the model at the output of each layer plus the initial embedding outputs.

        **attentions**: (`optional`, returned when ``config.output_attentions=True``)

            list of ``torch.FloatTensor`` (one for each layer) of shape ``(batch_size, num_heads, sequence_length, sequence_length)``:

            Attentions weights after the attention softmax, used to compute the weighted average in the self-attention heads.



    Examples::



        tokenizer = BertTokenizer.from_pretrained('bert-base-uncased')

        model = BertModel.from_pretrained('bert-base-uncased')

        input_ids = torch.tensor(tokenizer.encode("Hello, my dog is cute", add_special_tokens=True)).unsqueeze(0)  # Batch size 1

        outputs = model(input_ids)

        last_hidden_states = outputs[0]  # The last hidden-state is the first element of the output tuple



    """

    def __init__(self, config):

        super(BertModel, self).__init__(config)
        self.config = config
        self.embedding_dropout=nn.Dropout(p=0.2)
        self.embeddings = BertEmbeddings(config)
        self.encoder = BertEncoder(config)
        self.pooler = BertPooler(config)
        self.init_weights()



    def get_input_embeddings(self):
        return self.embeddings.word_embeddings



    def set_input_embeddings(self, value):
        self.embeddings.word_embeddings = value



    def _prune_heads(self, heads_to_prune):
        """ Prunes heads of the model.
            heads_to_prune: dict of {layer_num: list of heads to prune in this layer}
            See base class PreTrainedModel
        """

        for layer, heads in heads_to_prune.items():
            self.encoder.layer[layer].attention.prune_heads(heads)



    def forward(self, input_ids=None, attention_mask=None, token_type_ids=None, position_ids=None,
                head_mask=None, inputs_embeds=None, encoder_hidden_states=None, encoder_attention_mask=None):
        """ Forward pass on the Model.
        The model can behave as an encoder (with only self-attention) as well
        as a decoder, in which case a layer of cross-attention is added between
        the self-attention layers, following the architecture described in `Attention is all you need`_ by Ashish Vaswani,
        Noam Shazeer, Niki Parmar, Jakob Uszkoreit, Llion Jones, Aidan N. Gomez, Lukasz Kaiser and Illia Polosukhin.
        To behave as an decoder the model needs to be initialized with the
        `is_decoder` argument of the configuration set to `True`; an
        `encoder_hidden_states` is expected as an input to the forward pass.
        .. _`Attention is all you need`:
            https://arxiv.org/abs/1706.03762
        """
        if input_ids is not None and inputs_embeds is not None:
            raise ValueError("You cannot specify both input_ids and inputs_embeds at the same time")
        elif input_ids is not None:
            input_shape = input_ids.size()
        elif inputs_embeds is not None:
            input_shape = inputs_embeds.size()[:-1]
        else:
            raise ValueError("You have to specify either input_ids or inputs_embeds")
        device = input_ids.device if input_ids is not None else inputs_embeds.device
        if attention_mask is None:
            attention_mask = torch.ones(input_shape, device=device)
        if token_type_ids is None:
            token_type_ids = torch.zeros(input_shape, dtype=torch.long, device=device)

        # We can provide a self-attention mask of dimensions [batch_size, from_seq_length, to_seq_length]
        # ourselves in which case we just need to make it broadcastable to all heads.
        if attention_mask.dim() == 3:
            extended_attention_mask = attention_mask[:, None, :, :]
        elif attention_mask.dim() == 2:
            # Provided a padding mask of dimensions [batch_size, seq_length]
            # - if the model is a decoder, apply a causal mask in addition to the padding mask
            # - if the model is an encoder, make the mask broadcastable to [batch_size, num_heads, seq_length, seq_length]
            if self.config.is_decoder:
                batch_size, seq_length = input_shape
                seq_ids = torch.arange(seq_length, device=device)
                causal_mask = seq_ids[None, None, :].repeat(batch_size, seq_length, 1) <= seq_ids[None, :, None]
                causal_mask = causal_mask.to(torch.long)  # not converting to long will cause errors with pytorch version < 1.3
                extended_attention_mask = causal_mask[:, None, :, :] * attention_mask[:, None, None, :]
            else:
                extended_attention_mask = attention_mask[:, None, None, :]
        else:
            raise ValueError("Wrong shape for input_ids (shape {}) or attention_mask (shape {})".format(input_shape, attention_mask.shape))



        # Since attention_mask is 1.0 for positions we want to attend and 0.0 for

        # masked positions, this operation will create a tensor which is 0.0 for

        # positions we want to attend and -10000.0 for masked positions.

        # Since we are adding it to the raw scores before the softmax, this is

        # effectively the same as removing these entirely.

        extended_attention_mask = extended_attention_mask.to(dtype=next(self.parameters()).dtype)  # fp16 compatibility

        extended_attention_mask = (1.0 - extended_attention_mask) * -10000.0



        # If a 2D ou 3D attention mask is provided for the cross-attention

        # we need to make broadcastabe to [batch_size, num_heads, seq_length, seq_length]

        if self.config.is_decoder and encoder_hidden_states is not None:

            encoder_batch_size, encoder_sequence_length, _ = encoder_hidden_states.size()

            encoder_hidden_shape = (encoder_batch_size, encoder_sequence_length)

            if encoder_attention_mask is None:

                encoder_attention_mask = torch.ones(encoder_hidden_shape, device=device)



            if encoder_attention_mask.dim() == 3:

                encoder_extended_attention_mask = encoder_attention_mask[:, None, :, :]

            elif encoder_attention_mask.dim() == 2:

                encoder_extended_attention_mask = encoder_attention_mask[:, None, None, :]

            else:

                raise ValueError("Wrong shape for encoder_hidden_shape (shape {}) or encoder_attention_mask (shape {})".format(encoder_hidden_shape,

                                                                                                                               encoder_attention_mask.shape))



            encoder_extended_attention_mask = encoder_extended_attention_mask.to(dtype=next(self.parameters()).dtype)  # fp16 compatibility

            encoder_extended_attention_mask = (1.0 - encoder_extended_attention_mask) * -10000.0

        else:

            encoder_extended_attention_mask = None



        # Prepare head mask if needed

        # 1.0 in head_mask indicate we keep the head

        # attention_probs has shape bsz x n_heads x N x N

        # input head_mask has shape [num_heads] or [num_hidden_layers x num_heads]

        # and head_mask is converted to shape [num_hidden_layers x batch x num_heads x seq_length x seq_length]

        if head_mask is not None:

            if head_mask.dim() == 1:

                head_mask = head_mask.unsqueeze(0).unsqueeze(0).unsqueeze(-1).unsqueeze(-1)

                head_mask = head_mask.expand(self.config.num_hidden_layers, -1, -1, -1, -1)

            elif head_mask.dim() == 2:

                head_mask = head_mask.unsqueeze(1).unsqueeze(-1).unsqueeze(-1)  # We can specify head_mask for each layer

            head_mask = head_mask.to(dtype=next(self.parameters()).dtype)  # switch to fload if need + fp16 compatibility

        else:

            head_mask = [None] * self.config.num_hidden_layers



        embedding_output = self.embeddings(input_ids=input_ids, position_ids=position_ids, token_type_ids=token_type_ids, inputs_embeds=inputs_embeds)

#        print('EMD')

#        print(embedding_output.size())

#        print(embedding_output[0][1].norm())

#        print(embedding_output[0][1].size())

        embedding_output=self.embedding_dropout(embedding_output)

        encoder_outputs = self.encoder(embedding_output,

                                       attention_mask=extended_attention_mask,

                                       head_mask=head_mask,

                                       encoder_hidden_states=encoder_hidden_states,

                                       encoder_attention_mask=encoder_extended_attention_mask)

        sequence_output = encoder_outputs[0]

        pooled_output = self.pooler(sequence_output)



        outputs = (sequence_output, pooled_output,) + encoder_outputs[1:]  # add hidden_states and attentions if they are here

        return outputs  # sequence_output, pooled_output, (hidden_states), (attentions)





@add_start_docstrings("""Bert Model with two heads on top as done during the pre-training:

                       a `masked language modeling` head and a `next sentence prediction (classification)` head. """,

                      BERT_START_DOCSTRING,

                      BERT_INPUTS_DOCSTRING)

class BertForPreTraining(BertPreTrainedModel):
    r"""
        **masked_lm_labels**: (`optional`) ``torch.LongTensor`` of shape ``(batch_size, sequence_length)``:
            Labels for computing the masked language modeling loss.
            Indices should be in ``[-1, 0, ..., config.vocab_size]`` (see ``input_ids`` docstring)
            Tokens with indices set to ``-1`` are ignored (masked), the loss is only computed for the tokens with labels
            in ``[0, ..., config.vocab_size]``
        **next_sentence_label**: (`optional`) ``torch.LongTensor`` of shape ``(batch_size,)``:
            Labels for computing the next sequence prediction (classification) loss. Input should be a sequence pair (see ``input_ids`` docstring)
            Indices should be in ``[0, 1]``.
            ``0`` indicates sequence B is a continuation of sequence A,
            ``1`` indicates sequence B is a random sequence.
    Outputs: `Tuple` comprising various elements depending on the configuration (config) and inputs:
        **loss**: (`optional`, returned when both ``masked_lm_labels`` and ``next_sentence_label`` are provided) ``torch.FloatTensor`` of shape ``(1,)``:
            Total loss as the sum of the masked language modeling loss and the next sequence prediction (classification) loss.
        **prediction_scores**: ``torch.FloatTensor`` of shape ``(batch_size, sequence_length, config.vocab_size)``
            Prediction scores of the language modeling head (scores for each vocabulary token before SoftMax).
        **seq_relationship_scores**: ``torch.FloatTensor`` of shape ``(batch_size, sequence_length, 2)``
            Prediction scores of the next sequence prediction (classification) head (scores of True/False continuation before SoftMax).
        **hidden_states**: (`optional`, returned when ``config.output_hidden_states=True``)
            list of ``torch.FloatTensor`` (one for the output of each layer + the output of the embeddings)
            of shape ``(batch_size, sequence_length, hidden_size)``:
            Hidden-states of the model at the output of each layer plus the initial embedding outputs.
        **attentions**: (`optional`, returned when ``config.output_attentions=True``)
            list of ``torch.FloatTensor`` (one for each layer) of shape ``(batch_size, num_heads, sequence_length, sequence_length)``:
            Attentions weights after the attention softmax, used to compute the weighted average in the self-attention heads.
    Examples::
        tokenizer = BertTokenizer.from_pretrained('bert-base-uncased')
        model = BertForPreTraining.from_pretrained('bert-base-uncased')
        input_ids = torch.tensor(tokenizer.encode("Hello, my dog is cute", add_special_tokens=True)).unsqueeze(0)  # Batch size 1
        outputs = model(input_ids)
        prediction_scores, seq_relationship_scores = outputs[:2]
    """
    def __init__(self, config):
        super(BertForPreTraining, self).__init__(config)
        self.bert = BertModel(config)
        self.cls = BertPreTrainingHeads(config)
        self.init_weights()
    def get_output_embeddings(self):
        return self.cls.predictions.decoder
    def forward(self, input_ids=None, attention_mask=None, token_type_ids=None, position_ids=None, head_mask=None, inputs_embeds=None,
                masked_lm_labels=None, next_sentence_label=None):
        outputs = self.bert(input_ids,
                            attention_mask=attention_mask,
                            token_type_ids=token_type_ids,
                            position_ids=position_ids,
                            head_mask=head_mask,
                            inputs_embeds=inputs_embeds)

        sequence_output, pooled_output = outputs[:2]
        prediction_scores, seq_relationship_score = self.cls(sequence_output, pooled_output)
        outputs = (prediction_scores, seq_relationship_score,) + outputs[2:]  # add hidden states and attention if they are here

        if masked_lm_labels is not None and next_sentence_label is not None:
            loss_fct = CrossEntropyLoss(ignore_index=-1)
            masked_lm_loss = loss_fct(prediction_scores.view(-1, self.config.vocab_size), masked_lm_labels.view(-1))
            next_sentence_loss = loss_fct(seq_relationship_score.view(-1, 2), next_sentence_label.view(-1))
            total_loss = masked_lm_loss + next_sentence_loss
            outputs = (total_loss,) + outputs
        return outputs  # (loss), prediction_scores, seq_relationship_score, (hidden_states), (attentions)





@add_start_docstrings("""Bert Model with a `language modeling` head on top. """,
                      BERT_START_DOCSTRING,
                      BERT_INPUTS_DOCSTRING)
class BertForMaskedLM(BertPreTrainedModel):

    r"""

        **masked_lm_labels**: (`optional`) ``torch.LongTensor`` of shape ``(batch_size, sequence_length)``:

            Labels for computing the masked language modeling loss.

            Indices should be in ``[-1, 0, ..., config.vocab_size]`` (see ``input_ids`` docstring)

            Tokens with indices set to ``-1`` are ignored (masked), the loss is only computed for the tokens with labels

            in ``[0, ..., config.vocab_size]``

        **lm_labels**: (`optional`) ``torch.LongTensor`` of shape ``(batch_size, sequence_length)``:

            Labels for computing the left-to-right language modeling loss (next word prediction).

            Indices should be in ``[-1, 0, ..., config.vocab_size]`` (see ``input_ids`` docstring)

            Tokens with indices set to ``-1`` are ignored (masked), the loss is only computed for the tokens with labels

            in ``[0, ..., config.vocab_size]``



    Outputs: `Tuple` comprising various elements depending on the configuration (config) and inputs:

        **masked_lm_loss**: (`optional`, returned when ``masked_lm_labels`` is provided) ``torch.FloatTensor`` of shape ``(1,)``:

            Masked language modeling loss.

        **ltr_lm_loss**: (`optional`, returned when ``lm_labels`` is provided) ``torch.FloatTensor`` of shape ``(1,)``:

            Next token prediction loss.

        **prediction_scores**: ``torch.FloatTensor`` of shape ``(batch_size, sequence_length, config.vocab_size)``

            Prediction scores of the language modeling head (scores for each vocabulary token before SoftMax).

        **hidden_states**: (`optional`, returned when ``config.output_hidden_states=True``)

            list of ``torch.FloatTensor`` (one for the output of each layer + the output of the embeddings)

            of shape ``(batch_size, sequence_length, hidden_size)``:

            Hidden-states of the model at the output of each layer plus the initial embedding outputs.

        **attentions**: (`optional`, returned when ``config.output_attentions=True``)

            list of ``torch.FloatTensor`` (one for each layer) of shape ``(batch_size, num_heads, sequence_length, sequence_length)``:

            Attentions weights after the attention softmax, used to compute the weighted average in the self-attention heads.



    Examples::



        tokenizer = BertTokenizer.from_pretrained('bert-base-uncased')

        model = BertForMaskedLM.from_pretrained('bert-base-uncased')

        input_ids = torch.tensor(tokenizer.encode("Hello, my dog is cute", add_special_tokens=True)).unsqueeze(0)  # Batch size 1

        outputs = model(input_ids, masked_lm_labels=input_ids)

        loss, prediction_scores = outputs[:2]



    """

    def __init__(self, config):

        super(BertForMaskedLM, self).__init__(config)



        self.bert = BertModel(config)

        self.cls = BertOnlyMLMHead(config)



        self.init_weights()



    def get_output_embeddings(self):

        return self.cls.predictions.decoder



    def forward(self, input_ids=None, attention_mask=None, token_type_ids=None, position_ids=None, head_mask=None, inputs_embeds=None,

                masked_lm_labels=None, encoder_hidden_states=None, encoder_attention_mask=None, lm_labels=None, ):



        outputs = self.bert(input_ids,

                            attention_mask=attention_mask,

                            token_type_ids=token_type_ids,

                            position_ids=position_ids,

                            head_mask=head_mask,

                            inputs_embeds=inputs_embeds,

                            encoder_hidden_states=encoder_hidden_states,

                            encoder_attention_mask=encoder_attention_mask)



        sequence_output = outputs[0]

        prediction_scores = self.cls(sequence_output)



        outputs = (prediction_scores,) + outputs[2:]  # Add hidden states and attention if they are here



        # Although this may seem awkward, BertForMaskedLM supports two scenarios:

        # 1. If a tensor that contains the indices of masked labels is provided,

        #    the cross-entropy is the MLM cross-entropy that measures the likelihood

        #    of predictions for masked words.

        # 2. If `lm_labels` is provided we are in a causal scenario where we

        #    try to predict the next token for each input in the decoder.

        if masked_lm_labels is not None:

            loss_fct = CrossEntropyLoss(ignore_index=-1)  # -1 index = padding token

            masked_lm_loss = loss_fct(prediction_scores.view(-1, self.config.vocab_size), masked_lm_labels.view(-1))

            outputs = (masked_lm_loss,) + outputs



        if lm_labels is not None:

            # we are doing next-token prediction; shift prediction scores and input ids by one

            prediction_scores = prediction_scores[:, :-1, :].contiguous()

            lm_labels = lm_labels[:, 1:].contiguous()

            loss_fct = CrossEntropyLoss(ignore_index=-1)

            ltr_lm_loss = loss_fct(prediction_scores.view(-1, self.config.vocab_size), lm_labels.view(-1))

            outputs = (ltr_lm_loss,) + outputs



        return outputs  # (masked_lm_loss), (ltr_lm_loss), prediction_scores, (hidden_states), (attentions)





@add_start_docstrings("""Bert Model with a `next sentence prediction (classification)` head on top. """,

                      BERT_START_DOCSTRING,

                      BERT_INPUTS_DOCSTRING)

class BertForNextSentencePrediction(BertPreTrainedModel):

    r"""

        **next_sentence_label**: (`optional`) ``torch.LongTensor`` of shape ``(batch_size,)``:

            Labels for computing the next sequence prediction (classification) loss. Input should be a sequence pair (see ``input_ids`` docstring)

            Indices should be in ``[0, 1]``.

            ``0`` indicates sequence B is a continuation of sequence A,

            ``1`` indicates sequence B is a random sequence.



    Outputs: `Tuple` comprising various elements depending on the configuration (config) and inputs:

        **loss**: (`optional`, returned when ``next_sentence_label`` is provided) ``torch.FloatTensor`` of shape ``(1,)``:

            Next sequence prediction (classification) loss.

        **seq_relationship_scores**: ``torch.FloatTensor`` of shape ``(batch_size, sequence_length, 2)``

            Prediction scores of the next sequence prediction (classification) head (scores of True/False continuation before SoftMax).

        **hidden_states**: (`optional`, returned when ``config.output_hidden_states=True``)

            list of ``torch.FloatTensor`` (one for the output of each layer + the output of the embeddings)

            of shape ``(batch_size, sequence_length, hidden_size)``:

            Hidden-states of the model at the output of each layer plus the initial embedding outputs.

        **attentions**: (`optional`, returned when ``config.output_attentions=True``)

            list of ``torch.FloatTensor`` (one for each layer) of shape ``(batch_size, num_heads, sequence_length, sequence_length)``:

            Attentions weights after the attention softmax, used to compute the weighted average in the self-attention heads.



    Examples::



        tokenizer = BertTokenizer.from_pretrained('bert-base-uncased')

        model = BertForNextSentencePrediction.from_pretrained('bert-base-uncased')

        input_ids = torch.tensor(tokenizer.encode("Hello, my dog is cute", add_special_tokens=True)).unsqueeze(0)  # Batch size 1

        outputs = model(input_ids)

        seq_relationship_scores = outputs[0]



    """

    def __init__(self, config):

        super(BertForNextSentencePrediction, self).__init__(config)



        self.bert = BertModel(config)

        self.cls = BertOnlyNSPHead(config)



        self.init_weights()



    def forward(self, input_ids=None, attention_mask=None, token_type_ids=None, position_ids=None, head_mask=None, inputs_embeds=None,

                next_sentence_label=None):



        outputs = self.bert(input_ids,

                            attention_mask=attention_mask,

                            token_type_ids=token_type_ids,

                            position_ids=position_ids,

                            head_mask=head_mask,

                            inputs_embeds=inputs_embeds)



        pooled_output = outputs[1]



        seq_relationship_score = self.cls(pooled_output)



        outputs = (seq_relationship_score,) + outputs[2:]  # add hidden states and attention if they are here

        if next_sentence_label is not None:

            loss_fct = CrossEntropyLoss(ignore_index=-1)

            next_sentence_loss = loss_fct(seq_relationship_score.view(-1, 2), next_sentence_label.view(-1))

            outputs = (next_sentence_loss,) + outputs



        return outputs  # (next_sentence_loss), seq_relationship_score, (hidden_states), (attentions)





@add_start_docstrings("""Bert Model transformer with a sequence classification/regression head on top (a linear layer on top of

                      the pooled output) e.g. for GLUE tasks. """,

                      BERT_START_DOCSTRING,

                      BERT_INPUTS_DOCSTRING)

class BertForSequenceClassification(BertPreTrainedModel):

    r"""

        **labels**: (`optional`) ``torch.LongTensor`` of shape ``(batch_size,)``:

            Labels for computing the sequence classification/regression loss.

            Indices should be in ``[0, ..., config.num_labels - 1]``.

            If ``config.num_labels == 1`` a regression loss is computed (Mean-Square loss),

            If ``config.num_labels > 1`` a classification loss is computed (Cross-Entropy).



    Outputs: `Tuple` comprising various elements depending on the configuration (config) and inputs:

        **loss**: (`optional`, returned when ``labels`` is provided) ``torch.FloatTensor`` of shape ``(1,)``:

            Classification (or regression if config.num_labels==1) loss.

        **logits**: ``torch.FloatTensor`` of shape ``(batch_size, config.num_labels)``

            Classification (or regression if config.num_labels==1) scores (before SoftMax).

        **hidden_states**: (`optional`, returned when ``config.output_hidden_states=True``)

            list of ``torch.FloatTensor`` (one for the output of each layer + the output of the embeddings)

            of shape ``(batch_size, sequence_length, hidden_size)``:

            Hidden-states of the model at the output of each layer plus the initial embedding outputs.

        **attentions**: (`optional`, returned when ``config.output_attentions=True``)

            list of ``torch.FloatTensor`` (one for each layer) of shape ``(batch_size, num_heads, sequence_length, sequence_length)``:

            Attentions weights after the attention softmax, used to compute the weighted average in the self-attention heads.



    Examples::



        tokenizer = BertTokenizer.from_pretrained('bert-base-uncased')

        model = BertForSequenceClassification.from_pretrained('bert-base-uncased')

        input_ids = torch.tensor(tokenizer.encode("Hello, my dog is cute", add_special_tokens=True)).unsqueeze(0)  # Batch size 1

        labels = torch.tensor([1]).unsqueeze(0)  # Batch size 1

        outputs = model(input_ids, labels=labels)

        loss, logits = outputs[:2]



    """

    def __init__(self, config):

        super(BertForSequenceClassification, self).__init__(config)

        self.num_labels = config.num_labels

#        print(config.num_labels)

        self.bert = BertModel(config)

        self.dropout = nn.Dropout(config.hidden_dropout_prob)

        self.classifier = nn.Linear(config.hidden_size, config.num_labels)

        self.lossfn=focal_loss()

        self.init_weights()



    def forward(self, input_ids=None, attention_mask=None, token_type_ids=None,

                position_ids=None, head_mask=None, inputs_embeds=None, labels=None):



        outputs = self.bert(input_ids,

                            attention_mask=attention_mask,

                            token_type_ids=token_type_ids,

                            position_ids=position_ids,

                            head_mask=head_mask,

                            inputs_embeds=inputs_embeds)



        pooled_output = outputs[1]



        pooled_output = self.dropout(pooled_output)

        logits = self.classifier(pooled_output)

#        print(logits.size())

        outputs = (logits,) + outputs[2:]  # add hidden states and attention if they are here



        if labels is not None:

            if self.num_labels == 1:

                #  We are doing regression

                loss_fct = MSELoss()

                loss = loss_fct(logits.view(-1), labels.view(-1))

            else:

#                loss_fct = focal_loss()

                loss = self.lossfn(logits.view(-1, self.num_labels), labels.view(-1))

            outputs = (loss,) + outputs



        return outputs  # (loss), logits, (hidden_states), (attentions)





@add_start_docstrings("""Bert Model with a multiple choice classification head on top (a linear layer on top of

                      the pooled output and a softmax) e.g. for RocStories/SWAG tasks. """,

                      BERT_START_DOCSTRING,

                      BERT_INPUTS_DOCSTRING)

class BertForMultipleChoice(BertPreTrainedModel):

    r"""

        **labels**: (`optional`) ``torch.LongTensor`` of shape ``(batch_size,)``:

            Labels for computing the multiple choice classification loss.

            Indices should be in ``[0, ..., num_choices]`` where `num_choices` is the size of the second dimension

            of the input tensors. (see `input_ids` above)



    Outputs: `Tuple` comprising various elements depending on the configuration (config) and inputs:

        **loss**: (`optional`, returned when ``labels`` is provided) ``torch.FloatTensor`` of shape ``(1,)``:

            Classification loss.

        **classification_scores**: ``torch.FloatTensor`` of shape ``(batch_size, num_choices)`` where `num_choices` is the size of the second dimension

            of the input tensors. (see `input_ids` above).

            Classification scores (before SoftMax).

        **hidden_states**: (`optional`, returned when ``config.output_hidden_states=True``)

            list of ``torch.FloatTensor`` (one for the output of each layer + the output of the embeddings)

            of shape ``(batch_size, sequence_length, hidden_size)``:

            Hidden-states of the model at the output of each layer plus the initial embedding outputs.

        **attentions**: (`optional`, returned when ``config.output_attentions=True``)

            list of ``torch.FloatTensor`` (one for each layer) of shape ``(batch_size, num_heads, sequence_length, sequence_length)``:

            Attentions weights after the attention softmax, used to compute the weighted average in the self-attention heads.



    Examples::



        tokenizer = BertTokenizer.from_pretrained('bert-base-uncased')

        model = BertForMultipleChoice.from_pretrained('bert-base-uncased')

        choices = ["Hello, my dog is cute", "Hello, my cat is amazing"]

        input_ids = torch.tensor([tokenizer.encode(s, add_special_tokens=True) for s in choices]).unsqueeze(0)  # Batch size 1, 2 choices

        labels = torch.tensor(1).unsqueeze(0)  # Batch size 1

        outputs = model(input_ids, labels=labels)

        loss, classification_scores = outputs[:2]



    """

    def __init__(self, config):

        super(BertForMultipleChoice, self).__init__(config)



        self.bert = BertModel(config)

        self.dropout = nn.Dropout(config.hidden_dropout_prob)

        self.classifier = nn.Linear(config.hidden_size, 1)



        self.init_weights()



    def forward(self, input_ids=None, attention_mask=None, token_type_ids=None,

                position_ids=None, head_mask=None, inputs_embeds=None, labels=None):

        num_choices = input_ids.shape[1]



        input_ids = input_ids.view(-1, input_ids.size(-1))

        attention_mask = attention_mask.view(-1, attention_mask.size(-1)) if attention_mask is not None else None

        token_type_ids = token_type_ids.view(-1, token_type_ids.size(-1)) if token_type_ids is not None else None

        position_ids = position_ids.view(-1, position_ids.size(-1)) if position_ids is not None else None



        outputs = self.bert(input_ids,

                            attention_mask=attention_mask,

                            token_type_ids=token_type_ids,

                            position_ids=position_ids,

                            head_mask=head_mask,

                            inputs_embeds=inputs_embeds)



        pooled_output = outputs[1]



        pooled_output = self.dropout(pooled_output)

        logits = self.classifier(pooled_output)

        reshaped_logits = logits.view(-1, num_choices)



        outputs = (reshaped_logits,) + outputs[2:]  # add hidden states and attention if they are here



        if labels is not None:

            loss_fct = CrossEntropyLoss()

            loss = loss_fct(reshaped_logits, labels)

            outputs = (loss,) + outputs



        return outputs  # (loss), reshaped_logits, (hidden_states), (attentions)





@add_start_docstrings("""Bert Model with a token classification head on top (a linear layer on top of

                      the hidden-states output) e.g. for Named-Entity-Recognition (NER) tasks. """,

                      BERT_START_DOCSTRING,

                      BERT_INPUTS_DOCSTRING)

class BertForTokenClassification(BertPreTrainedModel):

    r"""

        **labels**: (`optional`) ``torch.LongTensor`` of shape ``(batch_size, sequence_length)``:

            Labels for computing the token classification loss.

            Indices should be in ``[0, ..., config.num_labels - 1]``.



    Outputs: `Tuple` comprising various elements depending on the configuration (config) and inputs:

        **loss**: (`optional`, returned when ``labels`` is provided) ``torch.FloatTensor`` of shape ``(1,)``:

            Classification loss.

        **scores**: ``torch.FloatTensor`` of shape ``(batch_size, sequence_length, config.num_labels)``

            Classification scores (before SoftMax).

        **hidden_states**: (`optional`, returned when ``config.output_hidden_states=True``)

            list of ``torch.FloatTensor`` (one for the output of each layer + the output of the embeddings)

            of shape ``(batch_size, sequence_length, hidden_size)``:

            Hidden-states of the model at the output of each layer plus the initial embedding outputs.

        **attentions**: (`optional`, returned when ``config.output_attentions=True``)

            list of ``torch.FloatTensor`` (one for each layer) of shape ``(batch_size, num_heads, sequence_length, sequence_length)``:

            Attentions weights after the attention softmax, used to compute the weighted average in the self-attention heads.



    Examples::



        tokenizer = BertTokenizer.from_pretrained('bert-base-uncased')

        model = BertForTokenClassification.from_pretrained('bert-base-uncased')

        input_ids = torch.tensor(tokenizer.encode("Hello, my dog is cute", add_special_tokens=True)).unsqueeze(0)  # Batch size 1

        labels = torch.tensor([1] * input_ids.size(1)).unsqueeze(0)  # Batch size 1

        outputs = model(input_ids, labels=labels)

        loss, scores = outputs[:2]



    """

    def __init__(self, config):

        super(BertForTokenClassification, self).__init__(config)

        self.num_labels = config.num_labels



        self.bert = BertModel(config)

        self.dropout = nn.Dropout(config.hidden_dropout_prob)

        self.classifier = nn.Linear(config.hidden_size, config.num_labels)



        self.init_weights()



    def forward(self, input_ids=None, attention_mask=None, token_type_ids=None,

                position_ids=None, head_mask=None, inputs_embeds=None, labels=None):



        outputs = self.bert(input_ids,

                            attention_mask=attention_mask,

                            token_type_ids=token_type_ids,

                            position_ids=position_ids,

                            head_mask=head_mask,

                            inputs_embeds=inputs_embeds)



        sequence_output = outputs[0]



        sequence_output = self.dropout(sequence_output)

        logits = self.classifier(sequence_output)



        outputs = (logits,) + outputs[2:]  # add hidden states and attention if they are here

        if labels is not None:

            loss_fct = CrossEntropyLoss()

            # Only keep active parts of the loss

            if attention_mask is not None:

                active_loss = attention_mask.view(-1) == 1

                active_logits = logits.view(-1, self.num_labels)[active_loss]

                active_labels = labels.view(-1)[active_loss]

                loss = loss_fct(active_logits, active_labels)

            else:

                loss = loss_fct(logits.view(-1, self.num_labels), labels.view(-1))

            outputs = (loss,) + outputs



        return outputs  # (loss), scores, (hidden_states), (attentions)





@add_start_docstrings("""Bert Model with a span classification head on top for extractive question-answering tasks like SQuAD (a linear layers on top of

                      the hidden-states output to compute `span start logits` and `span end logits`). """,

                      BERT_START_DOCSTRING,

                      BERT_INPUTS_DOCSTRING)

class BertForQuestionAnswering(BertPreTrainedModel):

    r"""

        **start_positions**: (`optional`) ``torch.LongTensor`` of shape ``(batch_size,)``:

            Labels for position (index) of the start of the labelled span for computing the token classification loss.

            Positions are clamped to the length of the sequence (`sequence_length`).

            Position outside of the sequence are not taken into account for computing the loss.

        **end_positions**: (`optional`) ``torch.LongTensor`` of shape ``(batch_size,)``:

            Labels for position (index) of the end of the labelled span for computing the token classification loss.

            Positions are clamped to the length of the sequence (`sequence_length`).

            Position outside of the sequence are not taken into account for computing the loss.



    Outputs: `Tuple` comprising various elements depending on the configuration (config) and inputs:

        **loss**: (`optional`, returned when ``labels`` is provided) ``torch.FloatTensor`` of shape ``(1,)``:

            Total span extraction loss is the sum of a Cross-Entropy for the start and end positions.

        **start_scores**: ``torch.FloatTensor`` of shape ``(batch_size, sequence_length,)``

            Span-start scores (before SoftMax).

        **end_scores**: ``torch.FloatTensor`` of shape ``(batch_size, sequence_length,)``

            Span-end scores (before SoftMax).

        **hidden_states**: (`optional`, returned when ``config.output_hidden_states=True``)

            list of ``torch.FloatTensor`` (one for the output of each layer + the output of the embeddings)

            of shape ``(batch_size, sequence_length, hidden_size)``:

            Hidden-states of the model at the output of each layer plus the initial embedding outputs.

        **attentions**: (`optional`, returned when ``config.output_attentions=True``)

            list of ``torch.FloatTensor`` (one for each layer) of shape ``(batch_size, num_heads, sequence_length, sequence_length)``:

            Attentions weights after the attention softmax, used to compute the weighted average in the self-attention heads.



    Examples::



        tokenizer = BertTokenizer.from_pretrained('bert-base-uncased')

        model = BertForQuestionAnswering.from_pretrained('bert-large-uncased-whole-word-masking-finetuned-squad')

        question, text = "Who was Jim Henson?", "Jim Henson was a nice puppet"

        input_text = "[CLS] " + question + " [SEP] " + text + " [SEP]"

        input_ids = tokenizer.encode(input_text)

        token_type_ids = [0 if i <= input_ids.index(102) else 1 for i in range(len(input_ids))]

        start_scores, end_scores = model(torch.tensor([input_ids]), token_type_ids=torch.tensor([token_type_ids]))

        all_tokens = tokenizer.convert_ids_to_tokens(input_ids)

        print(' '.join(all_tokens[torch.argmax(start_scores) : torch.argmax(end_scores)+1]))

        # a nice puppet





    """

    def __init__(self, config):

        super(BertForQuestionAnswering, self).__init__(config)

        self.num_labels = config.num_labels



        self.bert = BertModel(config)

        self.qa_outputs = nn.Linear(config.hidden_size, config.num_labels)



        self.init_weights()



    def forward(self, input_ids=None, attention_mask=None, token_type_ids=None, position_ids=None, head_mask=None, inputs_embeds=None,

                start_positions=None, end_positions=None):



        outputs = self.bert(input_ids,

                            attention_mask=attention_mask,

                            token_type_ids=token_type_ids,

                            position_ids=position_ids,

                            head_mask=head_mask,

                            inputs_embeds=inputs_embeds)



        sequence_output = outputs[0]



        logits = self.qa_outputs(sequence_output)

        start_logits, end_logits = logits.split(1, dim=-1)

        start_logits = start_logits.squeeze(-1)

        end_logits = end_logits.squeeze(-1)



        outputs = (start_logits, end_logits,) + outputs[2:]

        if start_positions is not None and end_positions is not None:

            # If we are on multi-GPU, split add a dimension

            if len(start_positions.size()) > 1:

                start_positions = start_positions.squeeze(-1)

            if len(end_positions.size()) > 1:

                end_positions = end_positions.squeeze(-1)

            # sometimes the start/end positions are outside our model inputs, we ignore these terms

            ignored_index = start_logits.size(1)

            start_positions.clamp_(0, ignored_index)

            end_positions.clamp_(0, ignored_index)



            loss_fct = CrossEntropyLoss(ignore_index=ignored_index)

            start_loss = loss_fct(start_logits, start_positions)

            end_loss = loss_fct(end_logits, end_positions)

            total_loss = (start_loss + end_loss) / 2

            outputs = (total_loss,) + outputs



        return outputs  # (loss), start_logits, end_logits, (hidden_states), (attentions)



class ERNIEForPreTraining(BertPreTrainedModel):
    """BERT model with pre-training heads.
    This module comprises the BERT model followed by the two pre-training heads:
        - the masked language modeling head, and
        - the next sentence classification head, and
        - the entity predict head.

    Params:
        config: a BertConfig class instance with the configuration to build a new model.

    Inputs:
        `input_ids`: a torch.LongTensor of shape [batch_size, sequence_length]
            with the word token indices in the vocabulary(see the tokens preprocessing logic in the scripts
            `extract_features.py`, `run_classifier.py` and `run_squad.py`)
        `token_type_ids`: an optional torch.LongTensor of shape [batch_size, sequence_length] with the token
            types indices selected in [0, 1]. Type 0 corresponds to a `sentence A` and type 1 corresponds to
            a `sentence B` token (see BERT paper for more details).
        `attention_mask`: an optional torch.LongTensor of shape [batch_size, sequence_length] with indices
            selected in [0, 1]. It's a mask to be used if the input sequence length is smaller than the max
            input sequence length in the current batch. It's the mask that we typically use for attention when
            a batch has varying length sentences.
        `masked_lm_labels`: masked language modeling labels: torch.LongTensor of shape [batch_size, sequence_length]
            with indices selected in [-1, 0, ..., vocab_size]. All labels set to -1 are ignored (masked), the loss
            is only computed for the labels set in [0, ..., vocab_size]
        `next_sentence_label`: next sentence classification loss: torch.LongTensor of shape [batch_size]
            with indices selected in [0, 1].
            0 => next sentence is the continuation, 1 => next sentence is a random sentence.

    Outputs:
        if `masked_lm_labels` and `next_sentence_label` are not `None`:
            Outputs the total_loss which is the sum of the masked language modeling loss and the next
            sentence classification loss.
        if `masked_lm_labels` or `next_sentence_label` is `None`:
            Outputs a tuple comprising
            - the masked language modeling logits of shape [batch_size, sequence_length, vocab_size], and
            - the next sentence classification logits of shape [batch_size, 2].

    Example usage:
    ```python
    # Already been converted into WordPiece token ids
    input_ids = torch.LongTensor([[31, 51, 99], [15, 5, 0]])
    input_mask = torch.LongTensor([[1, 1, 1], [1, 1, 0]])
    token_type_ids = torch.LongTensor([[0, 0, 1], [0, 1, 0]])

    config = BertConfig(vocab_size_or_config_json_file=32000, hidden_size=768,
        num_hidden_layers=12, num_attention_heads=12, intermediate_size=3072)

    model = ERNIEForPreTraining(config)
    masked_lm_logits_scores, seq_relationship_logits = model(input_ids, token_type_ids, input_mask)
    ```
    """
    def __init__(self, config):
        super(ERNIEForPreTraining, self).__init__(config)
        self.bert = BertModel(config)
        self.cls = BertEntityPreTrainingHeads(config, self.bert.embeddings.word_embeddings.weight)
        self.apply(self.init_bert_weights)

    def forward(self, input_ids, token_type_ids=None, attention_mask=None, masked_lm_labels=None, 
        input_ent=None, ent_mask=None, next_sentence_label=None, candidate=None, ent_labels=None):
        # the id in ent_labels should be consistent with the order of candidate.
        sequence_output, pooled_output = self.bert(input_ids, token_type_ids, attention_mask, input_ent, ent_mask,
                                                   output_all_encoded_layers=False)
        prediction_scores, seq_relationship_score, prediction_scores_ent = self.cls(sequence_output, pooled_output, candidate)
        if masked_lm_labels is not None and next_sentence_label is not None:
            loss_fct = CrossEntropyLoss(ignore_index=-1)
            masked_lm_loss = loss_fct(prediction_scores.view(-1, self.config.vocab_size), masked_lm_labels.view(-1))
            next_sentence_loss = loss_fct(seq_relationship_score.view(-1, 2), next_sentence_label.view(-1))
            ent_ae_loss = loss_fct(prediction_scores_ent.view(-1, candidate.size()[0]), ent_labels.view(-1))
            total_loss = masked_lm_loss + next_sentence_loss + ent_ae_loss
            original_loss = masked_lm_loss + next_sentence_loss
            return total_loss, original_loss
        else:
            return prediction_scores, seq_relationship_score, prediction_scores_ent